This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the dynamics of the aquifer and the standard dynamics of the storage capacity, and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-off between these two water harvesting techniques in an optimal control model. In particular, we show that, when these techniques are perfect substitutes, the development of RWH leads in the long run to a depletion of the water table, even if pumping is reduced. This result is illustrated by a numerical application for the Pecos River Basin (New Mexico, USA). JEL: Q25, C61, D61. / KEY WORDS: Rainwater Harvesting, Conjunctive Use, Groundwater Management, Optimal Control.
This is an introduction to the special section on financial frictions and debt constraints.
We study the finite-sample properties of tests for overidentifying restrictions in linear regression models with a single endogenous regressor and weak instruments. Under the assumption of Gaussian disturbances, we derive expressions for a variety of test statistics as functions of eight mutually independent random variables and two nuisance parameters. The distributions of the statistics are shown to have an ill-defined limit as the parameter that determines the strength of the instruments tends to zero and as the correlation between the disturbances of the structural and reduced-form equations tends to plus or minus one. This makes it impossible to perform reliable inference near the point at which the limit is ill-defined. Several bootstrap procedures are proposed. They alleviate the problem and allow reliable inference when the instruments are not too weak. We also study their power properties.
Considering extreme quantiles is a popular way to understand the tail of a distribution. While they have been extensively studied for univariate distributions, much less has been done for multivariate ones, primarily because there is no universally accepted definition of what a multivariate quantile or a multivariate distribution tail should be. In this paper, we focus on extreme geometric quantiles. In Girard and Stupfler (2014) "Intriguing properties of extreme geometric quantiles", their asymptotics are established, both in direction and magnitude, under suitable integrability conditions, when the norm of the associated index vector tends to one. In this paper, we study extreme geometric quantiles when the integrability conditions are not fulfilled, in a framework of regular variation.
The paper examines the monetary policy actions through which central banks in sub-Saharan Africa have tried to eliminate the negative impacts of the shocks facing their economies. We compare two different monetary policy regimes: a currency board regime (in the CFA zone) and an inflation targeting policy regime (Ghana and South Africa) when central banks respond to demand, supply, and fiscal shocks. We extend the usual forecasting and policy analysis system models to replicate the economic features of these economies during the period 2002–12 and to evaluate the impact of several policies in response to these shocks. We find that both policies are inappropriate in helping the economies escape from the effects of negative demand shocks, both are essential when negative shocks to primary balance occur, while inflation targeting dominates the currency board regime as a strategy to cope with positive shocks to inflation.
Imposing some constraints on public debt is often justified regarding sustainability and stability issues. This is especially the case when the ratio of public debt over GDP is restricted to be constant. Using a Ramsey model, we show that such a constraint can however be a fundamental source of indeterminacy, and therefore, of expectations-driven fluctuations. Indeed, through the intertemporal budget constraint of the government, income taxation negatively depends on future debt, i.e. on the expected level of production. This mechanism ensures that expectations on the future tax rate may be self-fulfilling. We show that this is promoted by a larger ratio of debt over GDP.
For several decades, researchers and policy makers have been almost unanimous in considering territorial development and local production systems as key concepts. Some notions have even played a leading role in the literature as well as in local action devices, such as districts, SPL, milieus, clusters, technopoles, and so on. Nowadays, understanding what relationship is at stake between industry and territory requires taking into account the changes that have occurred over time with regard to these local systems and their integration into the global evolution of contemporary economies. The aim of this paper is to assess and illustrate the way localized industrial systems, today most often referred to as «clusters», have grown in complexity and increasingly internalized contextual dimensions of environmental proximity, as well as societal topics related to local and global interactions between stakeholders. The introduction of these two variables is an invitation to go beyond the traditional framework and boundaries of industry and technological innovation, and to renew the local systems approach by applying it to business systems or industrial ecology dimensions.
This paper evaluates the most appropriate ways to model diffusion and jump features of high-frequency exchange rates in the presence of intraday periodicity in volatility. We show that periodic volatility distorts the size and power of conventional tests of Brownian motion, jumps and (in)finite activity. We propose a correction for periodicity that restores the properties of the test statistics. Empirically, the most plausible model for 1-min exchange rate data features Brownian motion and both finite activity and infinite activity jumps. Test rejection rates vary over time, however, indicating time variation in the data generating process. We discuss the implications of results for market microstructure and currency option pricing.
Using a laboratory experiment, we behaviourally study the impact of a sudden increase in the common-pool size on within-group conflict, i.e. , the paradox of the plenty. We also consider the potential role of governance in avoiding this paradox. In the first stage, a randomly-chosen leader of the group determines how much of the common-pool resource to protect from second-stage conflict. In the next stage, each group member allocates his private endowment between working or fighting for a share of the unprotected resource. We consider two treatments: anarchy (consisting of the second stage only) and with a leader deciding in the first stage. We find that the existence of institutions is not always better than anarchy. This is aggravated when the resource size is higher. Group conflict (income) decreases (increases) only when leaders chose the strongest resource protection. When leaders are malevolent, i.e. , they chose weak resource protection, outcomes are worse than when institutions are absent.
Bien que la prise en charge de personnes vivant avec le VIH (PVVIH) s’améliore globalement en Guyane, les disparités entre les régions et les différentes populations-clés sont importantes. Cet article a pour objectif de décrire les caractéristiques épidémiologiques, spatiales et cliniques des PVVIH suivies en zones isolées en les comparant avec celles suivies sur le littoral, dans les centres hospitaliers, en Guyane Française. Les données présentées reposent sur les données de suivi clinique réalisé au cours des missions délocalisées d’infectiologie au sein des Centres Délocalisés de Prévention et de Soins (CDPS) de Guyane. Ces données ont été analysées en relation avec les données INSEE issue du dernier recensement des communes de Guyane en 2012 et comparées aux données de suivi des PVVIH dans les différents centres hospitaliers de Guyane issues du logiciel Nadis®. L’évolution du taux annuel de découvertes de séropositivité VIH montre une arrivée plus tardive en zones isolées que sur le littoral de cette infection. L’épidémie apparait ces dernières années comme particulièrement active notamment chez les patients d’origine Brésilienne. L’âge médian des PVVIH en CDPS est de 43,8 ans, le sex ratio homme/femme est de 0,98. Prés de 37% des PVVIH sont dépistées au stade tardif (< 200 CD4/mm3). Le pourcentage de succès virologiques après 6 mois de traitement est de 80% par rapport à 88% sur le littoral. L’histoplasmose est la première cause d’infection opportuniste retrouvée. Les infections tropicales et notamment le paludisme (16%) sont fréquentes. La répartition spatiale des patients suivis montre une absence de PPVIH identifiées en amont des villes de Maripasoula et Saint Georges de l’Oyapock. Ces caractéristiques géographiques régionales rappellent l’importance de prendre en charge les PVVIH en zones isolées, particulièrement aux frontières, qui constituent des zones de passage, de repli, de prise de risques mais aussi de carence en offre de dépistage et de soins. Ainsi, en zones isolées en Guyane Française, les efforts doivent être poursuivis afin d’enrayer et de contrôler la diffusion de l’épidémie de VIH sur ces zones devenues stratégiques en terme de santé publique.